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The Big Bang: Fact or Fiction?. The Big Bang debate. A new perspective?. Dr Cormac O’Raifeartaigh. Is it finite? how big is it? Is it eternal? how old is it? How did it begin ?. Cosmology. The study of the cosmos. Not science?. Greek cosmology The geocentric universe. - PowerPoint PPT Presentation
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The Big Bang
The Big Bang: Fact or Fiction?
The Big Bang debateA new perspective?Dr Cormac ORaifeartaigh CosmologyIs it finite? how big is it?
Is it eternal? how old is it?
How did it begin?
The study of the cosmosNot science?Greek cosmologyThe geocentric universe
Centre of universeAll motion about earthAristotle (350 BC)
Ptolemy (200 AD) Earth motionlessEternal universe33 reasons gravity caused by suns mass
Newton (1642-1727) planet orbits due to gravityNewtons cosmology
Eternal, infinite universe attractive force
space, time fixedParadoxes? 20th cent astronomy: the galaxiespowerful telescopesphotographyEdwin Hubble (1889-1958)
1920s: many galaxies Cepheid variables stellar distances other galaxies
The expanding universe
Edwin Hubble (1889-1958)Far-away galaxies rushing away at a speed proportional to distancev = Hod1929: galaxies moving apart
Note: Doppler Effect
frequency of light depends on relative motion of observersRedshiftControversy?The origin of the universerewind Hubble graph
universe smaller in the past
extremely dense, extremely hot?
primeaval atom?
Fr Georges Lemaitre Expanding and cooling ever sinceLemaitre: Age of the universevelocity = distance / time but v = Ho d hence time = 1 / Ho
How long since BB? t~ 14 billion yrCo-produced model?Wrong estimate at first Reception (classical): nonsense! gravity pulls in not out
space is fixed
time has no beginning
Newton What is pushing out?What happened at time zero?How can U be younger than stars?
Isaac NewtonReception: general relativity space and time = spacetime spacetime affected by mass gravity = distortion of spacetime
Modern theory of gravity (1916)Einstein (1916)Evidence: orbit of Mercury, bending of starlightNote: not Kuhnian paradigm shiftReception (relativity): nonsense!space-time dynamic?Einstein: static universe (1917)Friedmann: expanding universe
Einstein vs Lemaitre:Apply Einsteins gravity to the cosmosgravity vs expansion1933: Einstein capitulates relativity supports BBsmall community only: pedagogyThe Big Bang model14 billion years ago, U concentrated in tiny volume
primordial explosion of matter, energy, space and time
U expanding and cooling ever since
Misnomer: singularity problemNot acceptedPredictions of Big Bang model1. The expansion of the U
2. Nucleosynthesis
3. The cosmic background radiation
1940s: nuclear physics
H, He nuclei (1 s) atoms (300,000 yr)
U = 75% H, 25% Heheavier atoms formed in starsconfirmed by HoyleGeorges Gamow (1906 1968)
nuclear fission nuclear fusion apply to Big Bang modelno impactBB prediction 3: microwave background
radiation from hot origin
released when atoms form recombination (300,000 yr)
radiation still observable?Alpher, Gamow and Herman
BB : superhot superdense beginninglow temp, microwave frequencyNo-one looked (1940s)Forgotten knowledgeInstead: steady-state model (1950s)New attack on BB
Expanding universe
Consistent with relativity BUTNo beginning
Matter continuously created
Fred Hoyle
Co-produced model?Deviation?Large impactSteady-State prediction: eternal U Continuous creation
Density of matter constant
U unchanging, eternal
Distant galaxies similar to present?
Youngest galaxies similar to present?
Falsification possibleAnswer: radio-astronomy (1960s)Ryle: radio sources Study most distant galaxiesStudy density and intensity
Density the same at all times? (SS)Or different? (BB)Answer: different
Cambridge3C survey
Martin RylePULSARS!Blow for SSRadio-astronomy: CMB (1965) radio-astronomy
microwave frequency
temperature 3 K
Echo of Big Bang!CMB observed accidentally
Penzias and WilsonGamow ignoredModern measurements of CMB
accurate measurements full spectrum perfect fit with theoryCOBE satellite (1992)Cosmic background radiation expected temperature expected frequency perfect blackbody spectrum
COBE (1992)Nobel Prize 2006 radiation quite uniform?1 in 10,000 galaxy formation?Cosmology TodayCosmic inflation (CMB)
Dark energy (CMB)
What happened at BB? Quantum gravity
Singularity at time zero?
Strong evidence for relativity Black holes, GPS
Hawking theorems
Revised Friedmann universesSummaryEvidence for BB model (expanding U 1929)Accepted by relativists (1933)Resisted by physics community
New avenues of evidence for BB (1948,49)Ignored by physics communityRise of rival SS model (1950)
Defeat of SS model (radiogalaxies, 1960)New evidence for BB (CMB 1965)Model gradually accepted (1968..)Latest: cyclic universe?